This invention relates to a family of new cathodoluminescent phosphors and to a method for preparing the novel phosphors.
In U.S. Pat. No. 2,462,547, there is described a family of phosphors consisting essentially of lanthanum oxysulfide containing two activators for example, europium and samarium. The phosphors of this family are infrared-stimulable storage phosphors; that is, they are useful for emitting light upon excitation with ultraviolet light and also emit upon subsequent stimulation with infrared light. These phosphors may be prepared by heating a mixture of lanthanum sulfate with suitable proportions of activator compounds in a reducing gas at about 800.degree. C.
An object of the invention is to provide new phosphors which are particularly useful for emitting light upon excitation with cathode rays.
Another object is to provide a method for preparing the novel phosphors.